274 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 18, 



the sea-level, and the result was the disturbance of the upper part of 

 the sand and the deposit of the fine gravel. Opening however to the 

 east, with much shelter from the rising ground in that direction, the 

 coast action would not be violent ; but the tidal action would be con- 

 siderable, for Hemingford would be the entrance to an inlet of 

 some magnitude, St. Neots being only 20 feet above the base of this 

 section. Hence the river deposits would be for the most part swept 

 away, and when the subsidence again gave way to elevation, the 

 valley would have nearly its present form. 



The surface soil, corresponding I presume with what Mr. Tiimmer 

 has called the warp of the drift, may have resulted from river action 

 in the last intermediate state ; but after the disturbing action of 

 plants, worms, and man, it is perhaps vain to endeavour to trace its 

 precise origin. Whether the same changes of level will explain the 

 phenomena of the valleys of the Cam and the Nar or of the Thames 

 itself, I leave to abler hands than mine to determine. 



May 18, 1853. 



Lord Moreton, M.P., was elected a Fellow. 

 The following communications were read : — 



1. Palichthyologic Notes. No. 4. — Ow ^Ae Affinities o/ Me 

 Genera Tetragonolepis and Dapeditjs. By Sir Philip de 

 Malpas Grey Egerton, Bart., M.P., F.R.S., F.G.S. &c. 



[Plate XL] 



Before entering upon the descriptions of the many new species of 

 fossil fishes which have accrued to the subfamily Lepidoidei homo- 

 cerci since the publication of the 'Poissons Fossiles,' it will be necessary 

 to consider the affinities of the genera Tetragonolepis and Bapedius, 

 arranged by Prof. Agassiz at the head of this subfamily, with reference 

 both to the relations they have to each other, and to the family in 

 which they are placed. Both these genera are adopted by Agassiz, 

 the former from Prof. Bronn, the latter from Sir Henry de la Beche, 

 but (although impressed with the conviction of the existence of the 

 two types) the Professor found the greatest difficulty in defining the 

 demarcation between them, and assigning to each its own generic 

 attributes. Bronn' s genus contained but one species, and that a 

 unique specimen from the Lias of Neidingen, in the cabinet of Baron 

 Althaus at Durheim, while Dapedius comprised all the fossil fishes 

 discovered in England that had any resemblance to the figure of 

 Dapedius politus published in the Geological Transactions. Among 

 the latter he found that some had the crowns of the teeth single, 

 while in others they were more or less notched, and he seized 

 upon this as the criterion between the genera, ranking all the single- 



